In a drive system for a printing roll or the like, it is possibly required to perform phase regulation between two rolls rotatingly driven by the same driving motor. Therefore, the applicant has proposed a phase regulating apparatus having a construction shown in FIG. 5, for example.
A phase regulating apparatus 1 shown in FIG. 5 performs phase regulation between printing rolls 2 and 3 rotatingly driven by the sa driving motor 4. The roll 2 is directly driven by the driving motor 4. The roll 3 is driven by the driving motor via a rotating force transmission path constituted of a gear train and a phase regulating speed reducer 5. The phase regulating speed reducer 5 is driven by a phase regulating motor 6.
The phase regulating speed reducer 5 is a differential gear unit, as which a wave gear drive is employed here. The phase regulating speed reducer 5 is constructed with annular rigid internal gears 51 and 52 arranged in parallel in coaxial condition, an annular flexible external gear 53 arranged at inside of the annular rigid internal gears, and a wave generator 54 engaged therein. The wave generator 54 has an elliptically shaped contour. By the wave generator, the flexible external gear 53 is deflected into an elliptic shaped configuration. Both end portions in major axis direction thereof are engaged with the rigid internal gears 51 and 52. When the wave generator 54 is rotated, the meshing positions are moved in circumferential direction.
Here, the number of teeth of the flexible external gear 53 and that of teeth of the rigid internal gear 51 are the same. In contrast to this, the number of teeth of the other rigid internal gear 52 is greater than those of the flexible external gear 53 and the rigid internal gear 51 by two. Therefore, when the wave generator 54 is driven to rotate and whereby the meshing points between the flexible external gear 53 and the rigid internal gears 51 and 52 are moved in circumferential direction, no relative rotation is caused between the flexible external gear 53 and the rigid internal gear 51 having the same number of gear teeth, whereas the other rigid internal gear 52 causes relative rotation with respect to these gears 53 and 51. As a result, a high speed rotation input to the wave generator 54 can be output with significant reduction depending upon a difference of number of gear teeth of the gears 52 and 53 from the rigid internal gear 51 or 52. The speed reducer of this type have been disclosed in U.S. Pat. No. 4,974,470.
In the phase regulating speed reducer 5 of this construction, the wave generator 54 is driven by a phase regulating motor 6. On the other hand, a gear 7 is rigidly fixed on the outer periphery of the rigid internal gear 51. This gear 7 is meshed with a gear 8 mounted on a rotary shaft 2a of the roll 2. Also, on the outer periphery of the other rigid internal gear 52, a gear 9 is rigidly fixed. The gear 9 is meshed with a gear 11 mounted on a rotary shaft 3a of the roll 3.
In the phase regulating apparatus 1, the phase regulating motor 6 is not driven for applying brake in normal operation. The roll 2 is driven by the driving motor 4. On the other hand, the roll 3 is driven by the driving motor 4 via gear trains 9 and 11 and via a transmission path reaching from the rotary shaft 2a of the roll 2 to the rotary shaft 3a of the roll 3 through gear trains 8 and 7, a phase regulating speed reducer 5 and the gear trains 9 and 11.
Next, at occurrence of necessity of phase adjustment for the roll 3 relative to the roll 2, the phase regulating speed reducer 5 is driven by the phase regulating motor 6.
As set forth above, conventionally, the wave gear drive is utilized as the phase regulating speed reducer for driving the speed reducer upon phase regulation to transmit rotation of the driving motor to the roll 3 side with slightly acceleration or deceleration for adjusting the phases between the rolls 2 and 3. On the other hand, when phase regulation is not necessary, a rotational force of the driving motor is transmitted to the roll 3 side via the speed reducer.
Here, in the conventional phase regulating apparatus, the speed reducer 5 is active even in normal operation to effect speed reducing operation. Accordingly, by appropriately setting number of gear teeth of the gear trains 8 and 7 on input side and gear trains 9 and 11 on output side, speed reducing operation of the speed reducer 5 is canceled.